This invention pertains to methods for converting signals representing trigonometric functions of angles to coded combinations of binary signals representing the angles.
In measuring the frequency of microwave signals, or the bearing angle of incoming radar signals, or the polarization of such signals, as well as phase differences, correlators are used. The outputs of the correlators are generally signals which are sine and cosine functions of a phase angle. At first these signals were displayed on a calibrated CRT display. As time progressed much greater accuracies were required.
The art started to move toward digital techniques. Typical devices as analog signal processors are shown in U.S. Pat. No. 3,800,221 issued Mar. 26, 1974. These signal processors while they satisfied the need were complex and cumbersome and created the demand for even better digitizers. Such a digitizer is shown in our copending application Ser. No. 70,687 filed Aug. 29, 1979, entitled ANGLE DIGITIZER. The present invention is an improvement in the use of such a digitizer to enhance its reliability when trying to measure the phase angles of signals when two different signals occur slightly time displaced with respect to each other. For example, in electronic warfare techniques quite often incoming radar signals from two different sources occurs very close together in time. Heretofore this phenomenon could cause a complete misreading of the frequency or bearing angle of each of the signals.